Well screens are generally used in subterranean wells in which it is desirable to extract well fluids such as oil, gas or water from the ground without bringing the debris, for example sand and other soil particulates, up with the fluid.
Conventionally, a well screen includes a length of perforated pipe known as a base pipe, one end of which is connected to a transportation pipe to transport the extracted fluid to the surface of the earth. A filter medium is disposed around the base pipe to prevent the debris in the fluid from entering the base pipe. A protective cover is further disposed around the filter layer to protect the filter medium from abrasion and impact while it is being run into a well bore. There is therefore a clearance (or gap) between the filter medium and the base pipe and/or between the filter medium and the protective cover to facilitate the assembly of the respective components of the well screen.